A backyard Tandoor oven

Build this version of an “Indian barbeque” for outdoor entertaining

By Robin Overall

Robin Overall cooking with the tandoor.

Since building the pizza oven as detailed in an earlier issue of The Shed , I have become more and more interested in different ways of cooking food. My pizza oven now produces a variety of breads and succulent roasts. As the oven sears the food with heat to seal in the flavours, it produces the succulence. Conventional cooking dries out food be-cause it is a relatively slow process. Those of you who built the pizza oven will know that the cooking process can be measured in seconds rather than hours.
My quest for different types of bread led me ultimately to Indian flatbreads. I have produced naan bread in the pizza oven but I want-ed to try the genuine method so I researched tandoori style food. This style of cooking was revived after the India/Pakistan division in 1947.The traditional cooking methods of the early Mogul dynasty had been retained only by peasant house-holds and almost disappeared. The shift to the east by people who fleeing the fighting included those who took their clay ovens with them.

Scribe pot cut-off.

Base cut

Takeaway
Traditional clay-oven cooking be-came popular in Britain during the 1950s and 1960s when Pakistani immigrants started restaurants and takeaway bars. A large section of the British population developed a taste for this style of cooking. This popularity has a lot to do with its taste but also it is a healthier way of cooking as all excess fat is drained off during cooking. Once you try it you will be hooked. It is not known as the “Indian barbecue” for nothing. It is an interesting addition to the outdoor living area and extends the range of food that can be cooked outdoors. It is also an easy project and will not break the bank in these cash-strapped times.
If you build a tandoor oven as an addition to the pizza oven you will have the perfect combination. When you empty the coals out of the pizza oven to commence baking, you will have a ready supply of charcoal for the tandoor.
The traditional tandoor is made in India by craftsmen working with relatively simple techniques. Soft clay is coiled on a large turntable and the surface is smoothed with paddles as the turntable slowly revolves. The clay mix varies some-what depending on the region. Most of the clays used all share a common factor of being reasonably open-pored. This helps to create an insulating layer to contain the heat. This porosity also helps in preventing the clay cracking when heated.

Oven forms in 44-gallon drum.

Concrete base.

Planter
As an ex-potter, I contemplated making one using these techniques but I am also a fully paid up member of the “don’t reinvent the wheel society”. Where was I able to lay my hands on a ready-made substitute? Well as any good sheddie knows, when in doubt go to the shed. In this case I went to the large red one. In the gardening department they had huge terracotta planters. “Would they do the trick?” I thought.
I selected one that was smooth on the inside and free of any blemish-es, cracks or other imperfections. Once it was safely home I set about modifying it.
I cut the base off using a 100 mm angle grinder fitted with a diamond blade. Use the serrated or ripple blade and not a smooth one as they can be used dry whereas the smooth ones have to be used wet. Mark the line to cut along by making a gauge block fitted with a pencil. Cut along the line going all around, increasing the depth of cut slowly until you are all the way through. Don’t try and cut all the way through in one spot and then move to the next, as this is a recipe for cracking the pot if ever there was.
Don’t forget to wear a mask when cutting terracotta as the dust is silica and a major lung irritant. After all we want you to enjoy your tandoor for many, many years to come.

Base of commons bricks...

...cemented in.

Best position
Here are a few pointers that might help you best position the tandoor. Smoke is not a problem—it is a charcoal-fuelled stove so only heat is produced. But have it near a table or bench so that prepared food and cooked food can be handy rather than your having to walk some dis-tance. Ideally you need to be able to get at your tandoor from all sides, not only when making it but also when placing and removing naan breads.
Make it a centre of interest.rather than an object tucked away in a corner. When not in use, it can make an attractive stand for pot plants, herb collection etc. Although the oven doesn’t weigh a great deal it is advisable to pour a thin concrete slab to start building on. This not only provides a level surface but also avoids weeds and plants growing over it. A slab as thin as 75 mm is ample with the odd coat hanger or similar thrown in as reinforcing.
Once this has cured (about two days) you can start building. I have used an old oil drum, which provides both a template to work to and a support for subsequent cladding. Without this the inexperienced builder will lose the pro-portions quickly and the thing will simply “not look right.” The oil drum needs to have the top and bottom removed and this is best done with a sharp chisel and club hammer.

Cutting drum
Work steadily around the top seam making small cuts. The seam will guide the chisel point. Don’t use an angle grinder or similar as it produces sparks. Sparks mean heat and there is a chance that any volatile residues left in the drum will mix with the air contained in the drum and be ignited, thereby exploding dangerously. The chisel method is quick and safe. When you get half-way round ensure that you have ear protection as the noise increases dramatically as the top is opened. You can now cut a small opening at the side of the drum and it is OK to use an angle grinder here, as the air ratio is now greater than any fumes contained in the drum because the top has been removed. This opening should measure approximately 200 mm high x 100 mm wide and will be flush with the internal base of the tandoor.
This is to allow air to get to the burning charcoal and occasionally to clean out ash. Position the drum on the cured slab and make sure the cut opening is easily accessible. The drum is held in position by having layers of bricks in the bottom. These are cemented in place with a very weak mix of cement/sand, that is one (1) part Portland cement to ten (10) parts course sand (builder’s sand). The addition of a little PVA to this mix makes it more workable.
As best you can, ensure that this base is level. This can be daunting as you are leaning down into the drum. (You could mark the position of the drum, remove it, lay your bricks and then replace the drum if you are accurate.)

Third course, using fire bricks.

Fourth course of “soldier” fire bricks. Note vital 400 mm measurement.

Ash and ventilation hole. Note gap in brick circle

Brick layers
The number of courses or brick layers could vary depending on the size of your pot.
I have used four layers of bricks altogether. For my pot, I have used four layers of bricks altogether. The bottom two layers of ordinary extruded bricks are laid dry and packed with a sand / cement mix that will harden in time. The third layer is firebricks laid flat. This is packed with sand only. The fourth layer is also firebrick and is stood on end with the flat face pointing inwards.
Mark the depth of your cut pot from the top of the drum, add 230 mm for the length of a fire brick laid soldier-fashion and this will give you a datum level to build up to.
The fourth layer of bricks consists of fire bricks laid “soldier” fashion, that is, standing on end. These bricks are not bonded together but simply butted up to each other. The drum keeps them in place and once a full circle is formed they are unable to move inwards.
An area needs to be left clear in the vertical brick circle for the ash removal hole. The hole in the side of the drum can be cut at this stage with an angle grinder and a thin cut-off blade. Fill the gaps between the soldier bricks and the drum with loose vermiculite.

Firebricks circle finished.

Pot installed.

Install planter
Carefully lower the planter in with the top rim of the pot positioned on the brick course. Adjust it so you have an even space all the way round between the pot and the drum.
This pot is not cemented in as the absence of cement means that all the components are floating, so to speak, and are free to move as they expand and contract. Pack a length of fibreglass rope between the drum and the pot rim.
The area between the planter pot and the drum is now filled with vermiculite. Use a medium grade. Simply pour this in and gently ram it down with your fingers until it is packed reasonably tightly. Stop filling when you are 100 mm from the top.
Lay strips of dampened newspaper over the vermiculite and then make up a ramming mix of the following: one (1) part Portland cement; one (1) part course sand (builder’s sand); five (5) parts fine scoria or pumice. These ingredients are obtainable from most hardware stores or garden centres.

Pot on fire brick ledge.

Cure
Make this into a moist mix that retains its shape when a lump is pressed in the hand. Press this in place gently tamping it until it is level with the top of the drum and pot.
Cover with a damp sack or similar and allow to cure for a couple of days.
When it is cured you can test-fire it prior to cladding the out-side. Light a very small fire in the middle with a few small twigs and paper. Gradually add charcoal until you have glowing charcoal covering an area about the size of a dinner plate. Place a sheet of something suitable over the top of your tandoor and leave until the fire dies.
Repeat this over the next few days while you are cladding the exterior.

Fibreglass expansion rope between drum and pot.

Cover
The space around the side opening needs to be fashioned so incoming air can be controlled. I have used the cast door from an old Pittsburgh potbelly heater. This is an area where the creative spirit within can shine. A simple opening plugged with a cut brick would suffice.
The outside of the drum now needs to be rendered as it is not a thing of beauty as it stands at present. Wrap hessian or old sacking around and hold in place with string or what-ever, while you wrap chicken wire around the whole structure. Cut through to expose the side opening.
Rendering is done in two stages, first a scratch coat and then a final coat. The scratch coat is simply cement mortar spread onto the wire/sacking surface so that the mortar squeezes through the wire and keys in. This mix is as follows: one (1) part Portland cement and six (6) parts builder’s sand.
The addition of a little PVA to this mix makes it more workable.

Robin Overall fills gap with vermiculite.

Gap backfilled

Render
Before the mix dries, scratch the surface in a series of horizontal lines with a homemade scratch comb. When this surface is dry, dampen it slightly and spread on the final render coat of: (one)1 part white cement; (one)1 part lime putty; six (6) parts silica sand. Lime putty is prepared by soaking a bag of builder’s lime (not garden lime) in a 20-litre pail of water and stirring daily for a couple of weeks until all the small particles of lime have been wetted. Mix the ingredients by volume and try to avoid adding extra water. Stirring with a paddle mixer in a power drill helps. The aim is to get a paste that can be spread with a sponge onto the scratch layer. This final render not only looks good but is totally waterproof.

Scratch comb used to key cement mortar.

Sacking and chicken wire cladding.

Cut tiles to fit

Tile top
The final task is to finish the top of the tandoor with tiles. These will need to be cut with a diamond saw in an angle grinder. The choice of tile is up to you but it needs to be fairly robust. Floor tiles are ideal. I have completed mine with river stones around the base to blend it into the gravel.
Your tandoor will require a lid to stop excess heat escaping. This can be made from sheet metal or wood with a heat resistant backing. I have actually used the cut-off base of the pot and a length of ti-tree for a handle. With the addition of two bolts, two short lengths of ½ inch copper pipe and some Araldite, a very attractive and suitably ethnic lid has been produced. The choice you make will depend on your imagination and ingenuity. Two key weapons in a true shed-die’s arsenal.

Firing up
Crumple a small amount of paper in the base and add a few sticks. Add lumps of charcoal and light. Gradually add charcoal until a glowing mass covers the base. The more fuel, the hotter it gets. It will burn for several hours on a full charge and reach temperatures in the region of 300° C. Very little attention is required to the fire and it will happily churn out heat all evening on very little fuel. As it turns out, I found pine cones to be an ideal fuel.

Tandoor fired.

TANDOOR RECIPE
The traditional foods cooked in a tandoor are tandoori chicken and naan bread.
The chicken is marinated in a mixture of tandoori paste/ acidophilus yoghurt/lemon juice for a couple of hours and then placed on long skewers (seekh). These are then placed in the tandoor with the lid partially covering the opening to retain heat.
Naan breads are rolled out to about 15 mm thick and then dampened slightly and placed on a naan cushion, damp side uppermost, and quickly slapped on the inside of the tandoor. This takes a bit of practice to get right without singeing all the hairs off your arm. When the breads are nicely browned and puffed up, remove them with the special tools comprising a small spatula ended rod and a hooked rod.

Naan bread (makes 10)
1 1/3 cups warm water
1 ½ tsp dried yeast
4 cups high-grade flour
2 tsp salt
4 cups yoghurt (plain)
¼ cup ghee (or melted butter)
1 tsp ground cumin